1. Technical Field
This invention relates to mechanical coupling devices in general, and to mechanical coupling devices that are hand operable in particular.
2. Background Information
Presently available coupling devices for selectively coupling shaft sections typically utilize an attachment mechanism such as an independent pin or key, screw threads, or a spring-loaded cylindrical, or spherical shaped, button. A problem with coupling devices that utilize an independent pin or key is that the pin or key is often misplaced and/or requires a tool for implementation. A problem with coupling devices that utilize screw threads is that if the application requires that the shaft be rotated, the threaded sections can become detached from one another. If a shaft section becomes decoupled in an inaccessible area (e.g., a chimney), the shaft section remaining in the inaccessible area can present a significant problem.
Presently available coupling devices that utilize spring-loaded cylindrical or spherical shaped buttons solve some of the problems associated with screw threads and pins, but they too have disadvantages or are limited in application. Spring-loaded cylindrical or spherical shaped button-type couplings are typically utilized on applications where the shafts to be coupled are thin wall type shafts; e.g., vacuum shaft sections. The button is mounted on the male portion of the coupling and is biased outwardly. Inserting the male portion of the coupling into the female portion causes the button to be deflected inwardly, thereby allowing the male portion to be received within the female portion. When the outwardly biased button encounters an aperture within the female portion, the button extends outwardly through the aperture in the thin wall of the female portion and thereby positively couples the male and female portions and the shafts attached thereto. The male and female portions can be decoupled by applying pressure from a finger on the button, pushing the button inwardly below the inner surface of the female portion. This manner of decoupling works well for thin wall applications because skin from the operator's finger will extend a distance into the aperture provided sufficient pressure is applied. The distance the finger extends into the aperture is substantially equal to or greater than the wall thickness of the female coupling portion.
Applications that require a stronger shaft and coupling device, particularly those where rotational torque is transmitted through the shaft, often utilize a thick wall coupling device. Some existing thick wall coupling devices utilize a spring mounted cylindrical button in the same manner as that described above. One problem with using a cylindrically shaped button in a thick wall coupling device application is that it becomes difficult or impossible to depress the button by finger (hereinafter “finger” shall be defined as any digit on a hand including a thumb) below because the finger skin only extends a limited amount into the aperture. Consequently, the finger by itself is unable to depress the button inwardly a distance sufficient to disengage the button from the aperture within the female portion. This is particularly true in applications where the operator is wearing work gloves that are less compliant than skin. In such cases, it becomes necessary to use a tool to depress the button the required distance. Another problem with using a cylindrical button in a cylindrical thick wall coupling device is that the button extending between the male and female portions carries any load torsionally or axially transmitted between shaft sections. As a result, the ability of the shaft sections to transmit a load is likely to be limited by the strength of the cylindrical button.